In a conventional wireless cellular communication network, there are clusters of adjoining coverage areas, known as cells. A base station device is positioned in a centralized or other location of each cell to serve wireless client devices in its cell. For example, the base station device is mounted on top of a pole or tower in order to transmit and receive signals above the ground. While deploying a base station in this manner is suitable for many geographical regions, it is not always suitable for deployment in an urban area where there are densely arranged buildings and other obstructions.
The ability to deploy a base station in an urban geographical environment or setting is more challenging for a variety of reasons. In general, installation of base station equipment is dictated by space availability and cost, and not by what will provide the best radio frequency (RF) coverage. There may be zoning restrictions that limit the ability to build a new tower, or in some cases, make it too expensive to do so. Likewise, in an urban setting, space availability on a building roof for new antenna installations may be limited. RF coverage planning is challenging in an urban setting due to the complexity of the physical geographical features created by densely populated buildings. Moreover, in an urban setting, transmitted RF signals propagate through “tunnels” created between buildings over streets, and not over the roofs of buildings. As a consequence of this tunneling effect, RF signals can propagate quite far along the streets causing inter-cell interference.
The concept of a “pico” or “mini” wireless base station has evolved in order to meet the challenges associated with deploying wireless network service in an urban environment. A pico base station has a smaller form factor than a standard base station and can therefore be installed on a building wall, pole, and other similar places, without the need for a tower or space on a roof. By design, a pico base station is configured to transmit with less power than that used by a standard base station and thus serves a smaller coverage area. The smaller sized base station can be installed in such a manner to better distribute RF transmissions around buildings, etc. Moreover, since the pico base station transmits at lower power, it can be installed in a wide variety of locations without violating power emission regulations. The pico base station can be built at a lower cost, making it attractive for massive deployment in a dense urban environment in order to achieve the higher capacity requirements associated with a densely populated urban area.
Deploying a pico base station has its challenges. Installation of a pico base station may be performed anywhere by any person, and not necessarily by an experience wireless system installer. Since the street morphology differs dramatically from one urban location to another and the installation may be made by non-experts to keep system deployment costs lower, there is no “one-size-fits-all” optimal RF radiation pattern that can configured for a base station device in order to achieve acceptable performance in a coverage area. Furthermore, maintaining a network of numerous pico base stations is a substantial effort. In a given urban setting, there may be thousands of pico base stations. It is a major challenge to optimize so many pico base stations for better coverage, capacity loading and carrier-to-interference (C/I) ratio across the entire network.